In recent years, it has been attempted that on a transparent substrate such as window glass for a vehicle such as an automobile or window glass for a house or building, an ultraviolet-absorbing film is formed as a coating film which has an ability to absorb ultraviolet rays entering into the vehicle or room therethrough and which has mechanical durability such as abrasion resistance.
In order to obtain an ultraviolet-absorbing coating film having high abrasion resistance and ultraviolet-absorbing ability, it has been attempted to form a silica-type ultraviolet-absorbing film on a substrate by using a coating solution having an organic ultraviolet-absorbing agent blended to a silane compound. For example, Patent Document 1 discloses that a coating solution comprising a silicon alkoxide and a water-soluble organic polymer such as polyethylene glycol and further containing an ultraviolet absorber or an organic colorant, is applied on a glass plate, followed by curing to obtain an ultraviolet-absorbing film made of an organic/inorganic composite film. However, with the silica-type ultraviolet-absorbing film as disclosed in Patent Document 1, absorption of long wavelength ultraviolet rays required by the present invention has not been accomplished although it has mechanical durability such as abrasion resistance, and if it is attempted to add the ultraviolet-absorber in a high concentration in order to absorb ultraviolet rays having long wavelengths, there have been problems such that deterioration in the mechanical durability and bleeding out of the ultraviolet absorber from the film under high humidity tend to occur, whereby the ultraviolet-absorbing ability cannot be maintained for a long period of time.
As a technique to solve the problem of bleeding out of the ultraviolet absorber in the silica type ultraviolet-absorbing film, Patent Document 2 discloses an attempt to form a silica-type ultraviolet-absorbing film by using a coating solution having blended to a silane compound a reaction product of a silane compound with an organic compound having an ultraviolet-absorbing ability. The silica-type ultraviolet-absorbing film as disclosed in Patent Document 2 is free from bleeding out of the ultraviolet absorber from the film and may accomplish absorption of the long wavelength ultraviolet rays desired by the present invention, but it has had a problem that cracking resistance and abrasion resistance are not sufficient especially when such a silica-type ultraviolet-absorbing film is formed on glass.
Therefore, an ultraviolet-absorbing film has been desired which is less susceptible to deterioration of the ultraviolet-absorbing ability by use for a long period of time, while securing mechanical durability such as abrasion resistance.